1. Field of the Invention
The present invention generally relates to image processing apparatus, and particularly relates to an information processing apparatus such as a digital copier that attends to inputting and outputting of image data. The present invention further relates to a job control method used in the information processing apparatus, a program for performing the method, and a record medium that stores the program therein.
2. Description of the Related Art
Image forming apparatuses of today are equipped with a function to process images to be printed. In such apparatuses, image data subjected to image processing is stored in a secondary memory device such as a hard disk drive. At the time of printing, image data is transferred from the secondary memory device to a semiconductor memory prior to the printing thereof.
As an example of such an image forming apparatus, a description will be given below in respect of Japanese Patent Laid-open Application No. 9-321962. Data-transfer speed of a hard drive decreases as access to a track shifts towards an inner track. When a hard drive is used as a frame memory for page printing in an image forming apparatus, image data transfer may be skipped with respect to areas where data-transfer speed is low.
In consideration of this, image data of great importance may be stored in an area where the data-transfer speed is high, thereby preventing the reproduction of images of great importance from having degraded image quality. To this end, a data storage control unit of this laid-open document divides the memory area of the hard drive into sub-areas having varying transfer rates, and stores image data of high importance in the sub-areas of high transfer rates after the compression/expansion unit compresses the image data.
In recent years, as the digitalization of copier machines advances further, processing and editing of image data have been made more often than before by utilizing the fact that image data is stored in memory. For example, image data corresponding to a plurality of document pages is stored in memory first, and is then output repeatedly to produce a required number of copies of the document. This is called an electronic sorting function, and eliminates a need for sorting of paper sheets after the printing.
The electronic sorting function requires the image data of a plurality of pages to be stored in memory, so that the use of the semiconductor memory alone as a page memory will result in an excessive memory cost As a result, a general configuration employs both the semiconductor memory (as page memory) and the storage-purpose memory (i.e., a secondary data storage), and a hard drive or the like that is less expensive than semiconductor memory devices is typically used as the storage-purpose memory.
In the secondary data storage, data is sequentially written in a given order, and is sequentially read in the same order. When data stored in the secondary data storage is to be printed, the following procedure will be performed:    (1) transfer of image data from the secondary data storage (e.g., hard drive) to the semiconductor memory (i.e., page memory); and    (2) outputting the image data of the semiconductor memory (page memory) to the printer unit.
In general, however, the transfer rate of the secondary data storage is slower than the image transfer rates of input/output operations, and the secondary data storage can only input a continuous stream of data having a certain data amount or output a continuous stream of data having a certain data amount. When images are to be printed, therefore, the time period required for the data transfer of the item (1) described above and the transfer timing thereof are important factors that need to be taken into consideration. Because of faster printing speed and more prevalent use of color printing in recent years, how to transfer image data from the secondary data storage to the semiconductor memory (i.e., page memory) as fast as it can at desired timing has become an important issue.
If the image data is not prepared before its use is required, the position of an image may be displaced on a transfer sheet, thereby creating the positional misplacement of an image. In the case of color printing, in particular, a miss copy may be produced that has MCYK colors displaced from each other.
Accordingly, there is a need for information processing apparatus for inputting and outputting image data that can perform processes at proper timing by controlling use of resources such as memory devices and scheduling jobs such as data outputting.